Not Applicable.
This invention relates to the design of movable sockets, for example, ball joints as used in automotive steering and suspension systems, and more particularly, to a movable socket configured with a spherical or part-spherical bearing surface and a projecting pin stud restrained within an elastomeric or spring-centered compliance bearing. The movable socket of the present invention is additionally configured to have increased durability under conditions of high load and misalignment and to be assembled using conventional techniques. While the present invention is described in detail with respect to automotive applications, those skilled in the art will recognize the broader applicability of the invention.
Conventional ball joints, and other movable sockets are used, for example, in automotive steering and suspension applications. The sockets comprise a housing having a circular cylindrical internal surface, a ball stud with a part-spherical ball head contained in the housing, and a synthetic resin or sintered alloy bearing member supporting the ball head within the housing. These components are commonly installed into the housing through a posterior opening, with the ball stud extending outward through an axially disposed anterior opening of a smaller diameter than the ball head. Traditionally, the posterior opening is closed by means of a cover-plate, spun, swaged, or welded in place. Once secured in place, the cover-plate presses on the bearing member either directly or indirectly through a resilient rubber intermediate component.
Several ball joint designs incorporating a projecting pin from the upper surface of the ball stud are shown in the prior art. These designs are intended to limit angular movement of the stud relative to the housing in which it is contained.
U.S. Pat. No. 3,790,195 issued to Edward J. Herbenar on Feb. 5, 1974 discloses a preloaded socket joint for an automotive steering linkage. The ""195 socket joint is primarily for rotational movement with a stud projecting from an internal cavity housing and having a part-spherical bulged section received in the housing and seated against a spherical face seat adjacent the projecting point of the stud from the housing. The stud further includes an axial extension beyond the half sphere within the housing which is received in a bearing with a resilient member entrapped between the wall of the cavity and the bushing. The opposite end of the housing cavity from the point of projection is closed by a cap which applies a preload to the axial end of the stud within the cavity and to the resilient member. As can be seen in FIG. 1 of the ""195 patent, all axial loads on the stud are transferred either directly through the stud itself to the cap which closes the housing, or through the bushing and resilient member to the cap.
U.S. Pat. No. 3,945,737 issued on Mar. 23, 1976, also to Edward J. Herbenar discloses a modification of the socket joint shown in the ""195 patent. The ""737 pivot joint provides a housing with a part-spherical bearing seat at one end thereof, a recessed closure cap secured in the other end thereof, and a stud having a shank projecting freely into the housing with a head tiltable on the seat. The stud further includes a tapered pin depending from the head and bottomed directly on the closure plate together with an axially split rubber bushing surrounding the pin and snugly seated in the housing. A wear take-up member between the closure plate and the bushing urges the bushing toward the head of the stud, and a ring surrounding the recess of the closure plate limits the tilting of the stud on the bearing seat. In this design, the compressive loads of the stud and the angulation loads of the stud are taken by the same member, i.e. the axially split, resilient bushing with a tapered bore. Thus, the design inhibits freedom in selecting an axial preload independently of angulation considerations and vice-versa.
U.S. Pat. No. 5,597,258 issued to Kincaid et al. on Jan. 28, 1997 discloses a preloaded pivot joint with a stud capable of rotation and angulation. The preloaded pivot joint is designed such that different internal components transfer the respective lateral loads, axial compression loads, and angulation loads experienced by the stud. Specifically, as seen in FIG. 1 of the ""258 patent, the stud incorporates a hemispherical portion for transferring lateral loads to a fixed bearing seat within the stud housing, a concentric convex tip for transferring compressive (axial) loads directly to a spring biased bearing seat, and a cylindrical extension between the hemispherical portion and the convex tip for radially transferring angulation loads to a hardened cylindrical metal ring of a resilient composite bushing.
Each of these prior art pivot sockets includes compliance components formed of a resilient material such as rubber, polyurethane, and the like, which surrounds a projection pin portion of the stud and which transfers some form of loading from the stud to the housing. Accordingly, it is highly advantageous to develop a preloaded pivot joint wherein a single compliance component transfers both axial and angulation loads to either the hardened housing walls or the end closure components, limiting the movement of the stud, but which does not carry lateral loads, reducing wear on the pivot socket components and extending the useful life thereof and which provides freedom in selecting an axial preload independently of stud angulation considerations.
Among the several objects and advantages of the present invention are:
The provision of a pivot socket employing a lower partially-spherical bearing surface to seat a stud having an axial extension within a housing cavity, and further employing a resilient component to surround the axial extension and to transfer axial load components from the bearing surfaces to end closure components;
The provision of the aforementioned pivot socket wherein the resilient component experiences little or no direct radial force when lateral forces are imparted to the stud;
The provision of the aforementioned pivot socket wherein the stud includes a partially spherical portion configured to seat against the lower partial spherical bearing surface;
The provision of the aforementioned pivot socket wherein the lower partial spherical bearing surface transfers lateral loads radially and axially from the partially spherical stud portion to the housing;
The provision of t he aforementioned pivot socket wherein a preload component transfers axial loads stud portion axially to the resilient component surrounding the axial extension of the stud;
The provision of the aforementioned pivot socket wherein the resilient component surrounding the axial extension of the stud extends from the end closure components to adjacent an upper surface of the preload component;
The provision of the aforementioned pivot socket wherein a preload component is interposed between the resilient component and the upper surface of the partially spherical stud portion;
The provision of the aforementioned pivot socket wherein the resilient component acts alone to provide both the axial preload between an upper spherical bearing and the lower partially spherical bearing, as well as providing resistance to angular displacement of the stud member; and
The provision of the aforementioned pivot socket wherein the configuration of the resilient component permits assembly of the pivot socket using conventional methods.
Briefly stated, a pivot socket of the present invention incorporates a stud shaft component having a part-spherical head portion disposed within a housing cavity, and an axial pin extension extending upward into the housing cavity. The part-spherical head portion is seated against a lower partial spherical bearing surface disposed within the housing cavity, and the axial pin extension is enclosed within a resilient cushion. During use, lateral or axial loads imparted on the stud shaft are transformed into radial and axial component forces at the bearing surface. The radial force components are transferred primarily to the interior walls of the housing cavity, while the axial force components are transferred axially through the resilient cushion to the end closure components secured to the housing. Little or no radial force components are transferred to the resilient cushion from lateral or axial loads imparted on the stud shaft, reducing wear on the pivot socket components and extending the useful life thereof.